R&D: Reconstruction of Non-Error Magnetic Hologram Data by Magnetic Assist Recording

Nature Scientific Reports as published an article written by Zen Shirakashi, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi, 441-8580, Japan, Taichi Goto, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi, 441-8580, Japan, and JST, PRESTO, 4-1-8 Honcho, Kawaguchi, Saitama, 332-0012, Japan, Hiroyuki Takagi, Yuichi Nakamura, Pang Boey Lim, Hironaga Uchida, and Mitsuteru Inoue, Toyohashi University of Technology, 1-1 Hibarigaoka, Tempaku, Toyohashi, Aichi, 441-8580, Japan.

A schematic diagram of thermomagnetic recording with the use of MA.
(a) Medium such as Bi:RIG magnetized perpendicularly in a single direction.
(b) Two incident beams, named signal beam and reference beam,
are radiated onto the medium, and the temperature distribution
of interference is formed by optical absorption and heating¹³.
The magnetization in the region where the temperature of the medium T
exceeds the Curie Temperature T _c is lost and (c) reversed by
the stray magnetic field (d) during the cooling process to form
the magnetic hologram fringe. In the MA recording,
the assist magnetic field is applied to the direction of reversed magnetization.

Abstract: “Hologram memory is expected to be the next-generation of optical data storage technology. Bismuth-substituted yttrium iron garnet is typically used for rewritable magnetic hologram media. The diffraction efficiency of magnetic holography depends on the Faraday rotation angle, but the experimental diffraction efficiency is not as high as that expected from calculations. This difference could be caused by incomplete magnetization reversal at the recorded region. In this study, we investigated the effects of magnetic assist (MA) recording through numerical simulation and experiment to improve the diffraction efficiency and the resulting reconstructed images. The improvement of diffraction efficiency was more effective in garnet films thinner than the width of a fringe, and a suitable value of the assist magnetic field was identified for the improvement. In addition, MA recording improved the intensity of reconstructed images and broadened the non-error recording conditions to the low energy region. This technique shows promise in improving the reconstructed quality of magnetic hologram data.“